Feedlot rearing versus pasture grazing enhances plasma leptin and insulin-like growth factor-1 concentrations but does not anticipate puberty in dairy buffalo (Bubalus bubalis) heifers

Plasma Leptin (LEP) and Insulin-like Growth Factor-1 (IGF-1), related to growth and puberty onset, were assayed in growing buffalo heifers from 8 up to 21 months of age, reared in feedlot (FR, n=13; initial body weight 132 ± 11 Kg) or grazing at pasture (PG, n = 13; 137 ± 12 Kg). Mean age at puberty was not different between the two groups (599.5 and 610.5 days, in FR and PG, respectively). At puberty, FR heifers showed higher BCS, and higher average daily weight gain (DWG) than PG ones (0.87 vs. 0.62 Kg/day), and were heavier (462 vs. 375 Kg). Negative correlation between DWG and age at puberty was significant for PG group. Plasma Inhibin-A increased in both groups one month before puberty. Plasma LEP and IGF-1 sharply increased 2 months before puberty (about 18 months old) in FR heifers only, which showed higher concentrations of both hormones than PG heifers. Plasma LEP levels correlated positively with body weight and IGF-1. Despite hormone levels were affected by rearing systems, being lower in heifers grazing at pasture, these latter experienced adequate growth and reproductive maturation. In fact, grazing heifers reached puberty at the same age of the feedlot reared ones, with shorter puberty–conception interval (51.3 vs. 67.2 days, for PG and FR groups, respectively) and no difference in conception rates (83.3 and 84.6%, for PG and FR groups respectively). The higher BW and DWG of FR heifers were due to body fat deposition, which did not anticipate the puberty onset.